docs: def _solve_base_feature_map(self, model_name, dependency_cache=None):
          """
          Solves the leaf :class:`revscoring.Feature` from the dependency for
          `model_name` using `dependency_cache`.  This will return a mapping
          between the `str` name of the base features and the solved values.
          """
          features = list(trim(self[model_name].features))
          feature_values = self.extractor.solve(features, cache=dependency_cache)
          return {str(f): v
                  for f, v in zip(features, feature_values)}